1. Field of the Invention
The instant invention is directed to a composition, processable into waterproofing membranes, having outstanding tear and weather resistance. More particularly, the instant invention is directed to an extrudable and calenderable elastomeric composition having high tear and weather resistance useful as a roofing membrane.
2. Description of the Prior Art
In recent years, a new class of elastomeric sulfonated polymers have been developed. These polymers are derived from polymeric materials having olefinic unsaturation, especially elastomeric polymers such as EPDM rubber. U.S. Pat. No. 3,642,728, incorporated herein by reference, teaches a method of selective sulfonation of olefinic unsaturation sites of an elastomeric polymer to form an acid form of a sulfonated elastomeric polymer. The olefinic sites of the elastomeric polymer are sulfonated by means of a complex of a sulfur trioxide donor and a Lewis base. The SO.sub.3 H groups of the sulfonated elastomer are readily neutralized with a basic material to form an ionically crosslinked elastomer having substantially improved physical properties over the corresponding unsulfonated elastomer at room temperature. However, these ionically crosslinked elastomers may be processed like a conventional thermoplastic at elevated temperatures under shear force in the presence of selected preferential plasticizers which dissipate the ionic associations at the elevated temperatures thereby creating a reprocessable elastomer.
The basic materials used as neutralizing agents are selected from organic amines or metallic bases in which the metal ion is selected from Groups I, II, III, IV, V, VIB, VIIB and VIII of the Periodic Table of Elements and mixtures thereof.
Further development of these sulfonated polymers is provided in U.S. Pat. No. 3,836,511, incorporated herein by reference, which teaches an improved process for the sulfonation of the olefinic sites of the elastomeric polymer. The patent discloses the use of an improved sulfonating agent selected from acetyl sulfate, propionyl sulfate and butyryl sulfate. The neutralizing agents employed to neutralize the acid form of the sulfonated elastomeric polymers are organic amines.
A still further development in this class of elastomeric sulfonated polymers is provided by U.S. Pat. No. 3,870,841, also incorporated herein by reference. This patent teaches a method of plasticization of the polymeric backbone of a neutralized sulfonated polymer by means of a polymer chain plasticizer which is a liquid compound having a boiling point of at least about 120.degree. F. The polymer chain plasticizer is selected from a dialkyl phthalate, a process oil or an organic ester.
A yet further development in elastomeric sulfonated polymers is disclosed in U.S. Pat. No. 3,847,854, incorporated herein by reference. This patent teaches a method of improving the processability of neutralized sulfonated elastomeric polymers by the addition of a preferential plasticizer which has at least one functional constituent which exhibits a bond moment whose absolute value is at least 0.6 Debyes, and must be a liquid at the desired processing temperature of the neutralized sulfonated elastomeric polymer. An example of an effective preferential plasticizer, as will be discussed hereinafter, is zinc stearate.
A still more recent improvement in sulfonated polymers is supplied by U.S. Pat. No. 4,222,914, incorporated herein by reference. U.S. Pat. No. 4,222,914 discloses an improved process for the sulfonation of olefinic sites on an elastomeric polymer and subsequent neutralization of the resulting polymer sulfonic acid to form a zinc sulfonate. The patent describes the reaction of a cement of the polymer with an acyl sulfate followed by neutralization with a solution of zinc acetate dissolved in methanol or an aqueous methanol solution.
Products resulting from the aforementioned methods for obtaining neutralized sulfonated elastomeric compositions possess either unsuitable rheological or physical properties necessary for the application of the present invention.
The present composition is directed to an application to which elastomeric products have recently been introduced. That is, the composition of this invention is proposed for use as a roof covering. Quite recently elastomeric extruded or calendered products have been developed for use in this market. When formulated with proper additives, certain thermosetting elastomeric compositions possess the excellent flexibility and weather resistance necessary for leak free, long term use. EPDM rubber, a thermosetting rubber, has been found to be useful as a roof covering. It possesses the proper degree of flexibility and weather resistance necessary for use in this application. However, thermosetting rubbers, such as EPDM, which possess the necessary flexibility and weather resistance, are difficult to install on a roof.
Installation requires seaming of the roofing panels on site to provide a continuous, leak free roofing surface. Since EPDM is a thermoset rubber, it cannot be heat sealed. Instead it is necessary to use adhesives to bind the seams. Not only are such adhesives expensive, but, more importantly, are time consuming to apply and are subject to delamination under stressful situations often encountered in roofing applications. Obviously, delamination results in leakage, i.e., roof failure.
On the other hand, the elastomeric sulfonated polymers discussed above are easy to handle. They, unlike thermosetting rubbers, can be heat sealed, thus negating the need for adhesives, so easily cover a roof. However, just as the products of the aforementioned patents are inadequate for use as a roofing composition, so too are the other disclosures in the prior art directed to elastomeric sulfonated polymers. None of them possess the properties necessary for a successful roofing material. Neither do any of the elastomeric sulfonated polymers of the prior art incorporate the combination of flexibility, weather resistance and tear resistance, properties necessary to produce a long lasting roof covering. Indeed, none of the disclosures of elastomeric sulfonated polymers in the prior art specifically disclose a composition useful as a roof covering. Moreover, none of them recite an elastomeric sulfonated composition whose constituents and concentrations would produce, when extruded or calendered, a membrane of the type required to cover roofs.
U.S. Pat. No. 4,157,992 discloses a composition which incorporates fillers and carbon black. However, this reference does not provide a composition of the type necessary for use as a roofing membrane. The composition of the '992 patent is recited as useful in the manufacture of footwear and garden hose. There is no disclosure or suggestion that the composition of this patent could be used as a roofing membrane.
U.S. Pat. No. 4,118,353 discloses a sulfonated elastomeric polymer which includes, as a necessary component, hydroxy alkyl carboxylate ester. This composition is recited to include a filler which may be carbon black and/or a mineral filler. In addition, the filler is recited to have a particle size range of between 0.03 and 20 microns. The composition of this invention does not include an hydroxy alkyl carboxylate ester. Moreover, the filler of the present invention is solely or substantially all carbon black.
It is important to note that hydroxy alkyl carboxylate ester can have deleterious effects on a sulfonated elastomeric polymer used as a roofing membrane. A roof covering is, of course, subject to elevated temperatures. The carboxylate ester at elevated temperatures can interact with the polymer to diminish its properties. Even at moderate temperatures the ester can bloom to the surface. This blooming diminishes heat sealability and adversely affects surface aesthetics.